1. Field of the Invention
The present disclosure relates to a receiver using impedance shaping.
2. Discussion of Related Art
In a frequency division multiple access method such as code division multiple access (CDMA) or frequency division-long term evolution (FD-LTE), receiver signals and transmitter signals are handled at the same time, and even in a time division multiple access method such as global system for mobile communication (GSM) or time division LTE (TD-LTE), receiver signals and transmitter signals are handled at a predetermined time interval. Thus, interference signals in receiver frequency band and/or transmitter signals in transmitter frequency band, act as the interference to a receiver. Here, in this disclosure, interference signals in a receiver band and transmitter leakage signals to a receiver band, may be collectively referred to as interference signals. In order to remove such interference signals, a surface acoustic wave (SAW) filter may be generally used. Electrical signals input through the SAW filter are converted into a mechanical wave in a piezoelectric device, the converted mechanical wave is delayed while being propagated along the device, and then the delayed mechanical wave is reconverted into the electrical signals by an electrode. Because of a configuration of such a SAW filter, the SAW filter may not be integrated in an integrated circuit (IC) to be implemented.
In addition, receiver signals and transmitter signals are combined at a duplexer, which has a limited transmitter to receiver isolation in a transmitter frequency band. Here, transmitter signals having a high power level of about 20 dBm or higher are leaked to the receiver port of the duplexer with its power being attenuated by 50 dB or lower. Receiver signals having a low power level of about −100 dBm or lower are received by a receiver terminal with transmitter leakage signals having a high power level of −25 dBm or higher, so that intermodulated signals are generated to cause degradation in receiver quality of the receiver terminal. In order to prevent performance degradation due to such intermodulated signals, a receiver terminal having high linearity is required. Such a receiver terminal may be generally implemented as a low noise amplifier (LNA) and a SAW filter. Here, generally, signals from a duplexer may be input to an LNA within an IC, output signals of the LNA may be input to the SAW filter positioned outside the IC, and then the output signals may be input to the IC again.
As described above, since the SAW filter cannot be integrated in an IC due to its structural characteristics, the output signals of the LNA should be input to the SAW filter outside the IC and the output signals of the SAW filter should be input to the IC again, and therefore signal characteristics are deteriorated and manufacturing process costs of a receiver terminal are increased.